so entirely privacy destroying and inherently vulnerable and insecure
(as of existing closed baseband systems, proprietary chipsets, poorly keyed, weakly ciphered, horribly authenticated, geo location and side channel leaking sieves we call handsets today that is...)
some have suggested the GTA04[0], which i do like, and also liked the original GTA01 back in the day. however, the ideal platform would be wideband SDR on a coreboot mobile with virtualization support (e.g. mobile Qubes OS with MIMO SDR radios and hardware protected key management)
one last comment on smart phones and mobile networks:
they do offer myriad and many methods to pollute the upstream; indications are this delays rather than defends, but still interesting and enjoyable none the less *grin*